Selected results
Measuring molecular frequencies in the 1--10 um range at 11-digits accuracy
We use the Italian fibre link network to transfer the microwave primary frequency standard from the Italian Metrological in Torino to the mid IR in our lab in Florence. We provide a generally applicable method for absolutely referencing mid IR light and we apply it to the measurement of a vibrational transition in a highly metastable state in a molecular beam experiment. [34]
Reviews
In a first article, the technology behind molecule chip is reviewed and a short history of its development is sketched. [30] In another article, we review the recent results in high-resolution spectroscopy on cold molecules. Laser spectroscopy of cold molecules addresses issues of symmetry violation, like in the search for the electric dipole moment of the electron and the studies on energy differences in enantiomers of chiral species; tries to improve the precision to which fundamental physical constants are known and tests for their possible variation in time and space; tests quantum electrodynamics, and searches for a fifth force. Further, we briefly review the recent technological progresses in the fields of cold molecules and mid-infrared lasers, which are the tools that mainly set the limits for the resolution that is currently attainable in the measurements.[32]
Characterization of OP-GaP crystal
We provide the first characterization of the linear, thermo-optic, and nonlinear properties of OP-GaP in a DFG configuration. Moreover, by comparing the experimental efficiency to Gaussian beam DFG theory, we derive an effective nonlinear coefficient d=17(3) pm/V for first-order quasi-phase-matched OP-GaP. The temperature and signal wavelength tuning curves are in qualitative agreement with theoretical modeling.[33]
Imaging molecules on a chip
We showed on-chip molecule detection, adding the final fundamental component to the molecule chip. We use REMPI, which is quantum-state selective, can be saturated with a few mJ/mm2 of laser light for most molecules, is intrinsically background-free, and is of general applicability. While in the simplest implementation of our detection scheme one would simply count the ions, we take the furthe rstep of using ion optics to create a time-resolved spatial image of the molecules.[26]
Vibrationally exciting molecules trapped on a microchip
Transitions between two vibrational quantum states can be induced while the molecules are trapped above the chip. We use CO molecules, prepared in the J = 1 rotational level of the a3Π1, v = 0 state and induce the transition to either the J = 1 or the J = 2 level in the vibrationally excited a3Π1, v = 1 state with pulsed, narrowband IR radiation. We can accurately model the transitions in the inhomogeneous and rotating field of the microtraps and we can address selectively a subset of molecules from our traps by choosing the appropriate polarization of the laser beam. [24]
Driving rotational transitions in molecules on a chip
We have coupled a coherent source of millimeter-wave radiation to our chip decelerator and measured a rotational spectrum of CO molecules that are less than 50 μm above the chip surface with a resolution of about half a MHz. We then used the millimeter-wave ratiation to switch the quantum state of selected molecules. We guided CO molecules in the J = 1 level of the a3Π1, v = 0 state to the center of the chip where they are released, pumped to the J = 2 level, recaptured, and guided off the chip.[19]
Suppression of non adiabatic losses of molecules from chip-based microtraps
We have demonstrated that metastable CO molecules, laser-prepared in the upper Λ-doublet component of the J = 1 level of the a3Π1, v = 0 state can be guided, decelerated, and trapped on a chip. In these experiments, non-adiabatic losses have been observed for 12C16O. In this most abundant carbon monoxide isotopologue, the low-field-seeking level and the non-field-seeking one become degenerate when the electric field strength goes to zero. Every time that the trapped molecules pass near the zero field region at the center of a microtrap, they can make a transition between these levels and thereby be lost from the trap. This degeneracy is lifted in 13C16O due to the hyperfine splitting. While hyperfine splitting cannot be varied, the degeneracy can be lifted by a variable amount in the 12C16O isotopologue by applying an external magnetic field. We have studied the non-adiabatic losses in metastable CO molecules confined in microtraps as a function of magnetic field strength and we compare quantitatively the data with the prediction of a theoretical model.[20]
An elliptical mirror for polar molecules
We developed and characterized a microstructured, electrostatic, elliptical mirror for polar molecules. This device consists of a set of interleaved thin electrodes to which alternating positive and negative voltages are applied to create a repulsive potential for molecules in low-field-seeking states. Such a mirror can be conveniently used to reshape the phase-space distribution of molecules from a molecular beam to better match the acceptance of the chip decelerator, thereby increasing the density of trapped molecules. Furthermore, the state selection provided by the mirror is expected to be an important advantage for future experiments.[21]